A Johns Hopkins University professor on Monday said there is an extremely low probability that public health is at risk during Harbor Point construction, where developers plan to pierce a protective cap over the 27-acre chromium-contaminated site.

The chromium dust generated by the manufacturing era of the former AlliedSignal site is a real concern, given it is a cancer-causing carcinogen, Hopkins environmental science professor Peter Lees said during a meeting called by Harbor Point opponent Stelios Spiliadis.

But it is also the type of carcinogen that only affects human health in high doses, which are unlikely to occur because readings on air monitors at the site would halt construction, and also because of the planned use of water misting to reduce dust at the site.

“I know people are thinking, ‘Oh my god, it’s a carcinogen, I’m going to die,’” said Lees, who has studied the effects of chromium on the 2,354 people who worked at AlliedSignal since 1950. “The risk of any disease related to the development of this site is going to be a function of the amount of hexavalent chromium that is aerosolized. I would put the probability of the risks of the release of any substantial, significant, harmful levels of chromium ­— workers at the site need to be concerned — but offsite the risk will just be very little.”

The meeting appeared to be aimed at raising more concern about development at the site. Organizer Spiliadis, who owns the Inn at the Black Olive adjacent to the site, has railed against piercing the protective cap, speaking during public meetings and City Council hearings held throughout the summer.

Lees, though, went on to say that even AlliedSignal workers he studied who had the lowest exposure to chromium dust showed no indication that they were any more at risk of lung cancer than the general population.

Even so, he said, the site needs to be closely monitored during construction, especially by using air monitoring for the release of chromium, which environmental regulators have pledged to conduct throughout the building of the Exelon Corp. regional headquarters scheduled to start early next year.

The Maryland Department of the Environment and the Environmental Protection Agency last week approved development plans, but Beatty Development Group LLC is still seeking approval of its air monitoring plan.

“It is incumbent upon the city, the contractor, everybody — we need to trust, but we need to verify,” Lees said. “I think there is a low probability significant amounts will be released but I think it’s incumbent upon anybody and everybody to watch the process.”

Erik Rifkin, an environmental scientist and former director of the National Aquarium, said that the developer has a huge incentive to assure there are no air monitoring readings showing chromium escaping the site. If that happens, and regulators stop construction, “all hell is going to break loose,” he said.

“After all these assurances and you get a reading, then you’re going to have every environmental group in here and it’s going to be hard to restart the process,” Rifkin said.

Stelios said during the meeting that he intends to continue organizing concerned citizen groups and press MDE and EPA officials to remain in constant communication about construction at the site.